• What are the three parts that make up atoms?

• Which of the three are most important in determining what element an atom is?

• Which of the three are most important in determining how an element reacts with other elements?

S-88Students will investigate our current understanding of the atom.

• What is the charge on each of the following parts of the atom?

• Proton• Neutron• Electron

S-89Students will investigate our current understanding of the atom.

SPS1 Students will investigate our current understanding of the atom.SPS2 Students will explore the nature of matter, its classifications, and

its system for naming types of matter.SPS6 Students will investigate the properties of solutions.

Chapter 2

Properties of Matter

Why are elements and compounds classified as pure substances?How do mixtures differ from pure substances?What is the main difference among solutions, suspensions, and colloids?

2.1 Classifying Matter

• Pure substance – matter that always has the same compositions– Same number of

elements– Combined the same

way – Has the same

properties – Either elements or compounds

2.1 Classifying MatterWhy are elements and compounds classified as pure substances?

Glucose

• Element – can not be broken down chemically– Atom – smallest particle of an element– Found on the periodic table– Different elements have different atoms– Elements are represented by symbols

made of one of two letters– First is a Capital letter, second lower

case

2.1 Classifying MatterWhy are elements and compounds classified as pure substances?

• Compounds – made of two or more elements combined chemically– Same elements in the same ratio

combined in the same pattern– Very different property from the

elements that make them– Table Salt

• Sodium – silver metal that explodes on contact with water

• Chlorine – poisonous gas

2.1 Classifying MatterWhy are elements and compounds classified as pure substances?

• Mixture – two substances that are combine with no fixed composition– Not chemically combined– Can be

• Heterogeneous Mixture – parts of the mixture are noticeably different from one another

– Sand, muddy water, soil, granite

• Homogeneous Mixture – (solution) parts are evenly distributed

– Alloys, salt water, peroxide solution

2.1 Classifying MatterHow do mixtures differ from pure substances?

• Mixtures can be classified by the size of the largest particles– Solution – very small particles – this is a

homogeneous mixture– Suspension – large particles – a

heterogeneous mixture that separates into layers over time

– Colloid – intermediate size particles – do not separate into layers, but scatter light like a suspension

2.1 Classifying MatterWhat is the main difference among solutions, suspensions, and colloids?

2.1 Classifying Matter

What are some examples of physical properties?How can knowing the physical properties of matter be useful?What processes are used to separate mixtures?

2.2 Physical Properties

• Physical property – can be observed or measured without changing the composition of the substance– Viscosity – the resistance of a liquid to flow– Conductivity – ability to allow heat to flow– Malleability – ability to be hammered

without shattering or breaking– Hardness – how difficult it is to scratch a

substance

2.2 Physical PropertiesWhat are some examples of physical properties?

• Physical property – Melting and Boiling Points– Density – mass divided by volume

2.2 Physical PropertiesWhat are some examples of physical properties?

• Physical properties are used to– Identify materials – items are tested and

compared to known properties– Choose materials for specific purposes –

based on what properties are needed

2.2 Physical PropertiesHow can knowing the physical properties of matter be useful?

• Physical properties are used to– Separate the substances in a mixture

• Filtration – separation based on size of particles• Distillation – separation based on differences in

boiling points

• Physical change – when some of the properties of a substance change, but the substance remains the same– Sharpening a pencil, melting ice, cutting

hair

2.2 Physical PropertiesWhat processes are used to separate mixtures?

When can chemical properties be observed?What observations might indicate that a chemical change has occurred?What is the difference between chemical and physical changes?

2.3 Chemical Properties

• Chemical Property – the potential of a substance to undergo a reaction– Can only be observed when the

substance undergoes the reaction

• Examples– Flammability – ability to react with

oxygen– Reactivity – how a substances combines

chemically with another substance

2.3 Chemical PropertiesWhen can chemical properties be observed?

• Three common signs that a chemical change has occurred – Change in color – Production of a gas– Formation of a precipitate

• Precipitate – solid formed when two liquids are mixed

2.3 Chemical PropertiesWhat observations might indicate that a chemical change has occurred?

• How to tell if the change is chemical or physical– Chemical change – the substance changes

• New chemical properties• Some new physical properties

– Physical change – the substance stays the same• Same chemical properties• Same intrinsic chemical properties

– Intrinsic – those that can be used to identify the substance– Density, conductivity, viscosity

2.3 Chemical PropertiesWhat is the difference between chemical and physical changes?